Method and an apparatus for cleaning internal combustion engine crankcase blow-by-gas and an internal combustion engine including said apparatus

ABSTRACT

An internal combustion engine in which the oil content of blow-by gas is reduced by conveying the blow-by gas (34) away from the engine to be cooled in a heat exchanger (30). Oil (40) condensing from the cooled blow-by gas (34) is returned to the engine and the cooled blow-by gas is exhausted to atmosphere or conveyed to the engine air intake system.

BACKGROUND OF THE INVENTION

The present invention relates to a method and an apparatus for cleaninginternal combustion engine crankcase blow-by gas and an internalcombustion engine including said apparatus.

1. Field of the Invention

During the compression and power strokes in an internal combustionengine, the difference in gas pressures above and below a piston issufficient to cause leakage (blow-by) of gas past the piston into theengine crankcase. The resulting increase in pressure within thecrankcase can cause oil to pass by the engine oil seals and thispressure may also damage the seals.

To diminish the damaging effects of blow-by it is normal to relievecrankcase pressure by either venting the blow-by gas to atmosphere viaan open breather or by connecting the crankcase to the engine intake airsystem whereby blow-by gas is conveyed to the air intake system andthence to the combustion chamber under the control of a pressureregulating valve. The pressure regulating valve maintains gas pressurewithin the crankcase between desirable limits. This latter arrangementconstitutes a closed-circuit breather system.

The blow-by gas carries with it oil vapour and this exits the engine toatmosphere via the open breather or, in the closed-circuit breathersystem, is taken into the engine air inlet system and is partially orfully burned before exiting to atmosphere via the engine exhaust system.In either case, this results in undesirable emissions being emittedwhich contain either unburned oil or the products of burned oil. The oilcontent of the blow-by gas, where this is fed into the engine intake airsystem via a closed-circuit breather system, also leads to fouling ofturbo-charger compressor vanes, engine poppet valves and othercomponents in contact with inlet air.

2. Description of the Related Art

U.S. Pat. No. 3,533,385 and JP-A-61-171814 each disclose an apparatusfor reducing the oil content of blow-by gas in an internal combustionengine, comprising: means for conveying blow-by gas away from the enginecrankcase to a heat exchanger cooled by air from an engine air intakesystem, said blow-by gas being cooled by passing it through the heatexchanger; means for returning oil condensed from said cooled blow-bygas to the engine; and means for directing the cooled blow-by gas intothe flow of engine inlet air, said means comprising a blow-by gasoutlet.

In the case of U.S. Pat. No. 3,533,385, the blow-by gas outlet islocated internally of the heat exchanger but is not adjacent to an airinlet end of the heat exchanger.

In the case of JP-A-61-171814, the blow-by gas outlet is external of theheat exchanger.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method of reducingoil content of blow-by gas in an internal combustion engine.

It is a further object of the present invention to provide an apparatusfor reducing oil content of blow-by gas in an internal combustionengine.

A yet further objective is to provide a means for the recovery oflubricating oil which would otherwise be lost to atmosphere or burned inthe engine combustion chamber.

According to one aspect of the present invention, there is provided amethod of reducing the oil content of blow-by gas in an internalcombustion engine, comprising the steps of: conveying blow-by gas awayfrom the engine crankcase to a heat exchanger cooled by air from anengine air intake system; cooling said blow-by gas by passing it throughsaid hear exchanger; returning oil condensed from said cooled blow-bygas to the engine; and directing said coled blow-by gas into the flow ofengine inlet air via a blow-by gas outlet located internally of the heatexchanger, characterised in that said blow-by gas outlet is locatedadjacent to an air inlet end of said heat exchanger.

According to a second aspect of the present invention, there is providedan apparatus for reducing the oil content of blow-by gas in an internalcombustion engine, comprising: means for conveying blow-by gas away fromthe engine crankcase to a heat exchanger cooled by air from an engineair intake system, said blow-by gas being cooled by passing it throughthe heat exchanger; means for returning oil condensed from said cooledblow-by gas to the engine; and means for directing the cooled blow-bygas into the flow of engine inlet air, said means comprising a blow-bygas outlet, located internally of the heat exchanger, characterised inthat said blow-by gas outlet is located adjacent to an inlet air end ofsaid heat exchanger.

Further features of the method and apparatus of the invention are inaccordance with the appended claims.

According to a third aspect of the present invention there is providedan internal combustion engine incorporating an apparatus in accordancewith the second aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and further features of the present invention will be morereadily understood from the following description of a preferredembodiment, by way of example thereof, with reference to theaccompanying drawings, of which:

FIG. 1 is a schematic illustration of an internal combustion engineincluding an apparatus for reducing the oil content of blow-by gas;

FIG. 2 is a schematic illustration of an internal combustion engineincluding an apparatus in accordance with a preferred embodiment of thepresent invention;

FIG. 3 is a longitudinal-sectional view in a vertical plane of a heatexchanger for use in the apparatus of the preferred embodiment of theinvention;

FIG. 4 is a cross-sectional view on vertical section line A--A of FIG. 3illustrating the arrangement of tubular members within a housing of theheat exchanger;

FIG. 5 is a cross-sectional view on vertical section line A--A of FIG. 3showing a similar arrangement to that of FIG. 4 of alternative tubularmembers within the housing of the heat exchanger;

FIGS. 6a to c are plan views of partition plates for the heat exchangerof FIG. 3 incorporating the tubular member arrangement of FIG. 5;

FIG. 7 is a longitudinal-sectional view in a vertical plane of a secondembodiment of a heat exchanger; and

FIG. 8 is a longitudinal-sectional view in a vertical plane of a thirdembodiment of a heat exchanger.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, FIG. 1 is a schematic illustration of aninternal combustion engine 10 including an apparatus 12 for cleaningcrankcase blow-by gas. The internal combustion engine 10 is of theoverhead camshaft type and has a crankcase 14, an oil sump 16, an inletair manifold 8 for conveying air to a combustion chamber 20 disposedabove a piston 22, an exhaust manifold 24 for conveying exhaust gas awayfrom said combustion chamber 20 and a rocker arm housing 26 containing arocker arm and camshaft arrangement 28.

The apparatus 12 for cleaning blow-by gas comprises a heat exchanger 30located in the engine air intake system with its air outlet 30aconnected to the engine air manifold 18 and its inlet 30b connectingwith an outlet of an air filtering means (not shown) of said air intakesystem. The apparatus 12 also includes a pipe 32 for conveying blow-bygas 34 from the engine crankcase 14 to a blow-by gas inlet 30c of theheat exchanger 30 and an oil return pipe 36 connecting the oil sump 16with an oil outlet 30d of said heat exchanger 30. The heat exchanger 30also includes a blow-by gas outlet 30e.

During engine operation, oil within the engine sump 16 becomes hot anddue to mechanical agitation by rotation of the crankshaft 38 some of theoil exists as a hot mist/vapour coating engine components within thecrankcase 14 and contaminating blow-by gas which leaks into thecrankcase 14. The blow-by gas increases pressure within the crankcase 14and ordinarily this pressure would be released by exhausting the gas toatmosphere through an open breather or alternatively conveying said gasto the engine air inlet manifold under the control of a pressureregulating means.

The blow-by gas from the crankcase 14 is conveyed to the heat exchanger30 where it is cooled. Cooling of the blow-by gas causes some of the oilvapour contained therein to condense and the condensed oil 40 iscollected and returned to the engine 10. The oil 40 is returned to theengine sump 16 by the oil return pipe 36 and enters said sump 16 belowthe oil level 42. The "cleaned" blow-by gas is exhausted to atmosphere.

It will be appreciated that the heat exchanger 30 can be cooled by anysuitable cooling agent, but it is preferred that the heat exchanger 30is cooled by air 42 from the engine air inlet system thus providing asimple and inexpensive method of cooling the blow-by gas.

FIG. 2 is a schematic illustration of an internal combustion engineincluding an apparatus in accordance with a preferred embodiment of thepresent invention. In the following description, like numerals will beused to denote like parts.

This embodiment differs from that illustrated in FIG. 1 insofar that theblow-by gas outlet 30e of the heat exchanger 30 is internal to the heatexchanger 30 and directs cooled blow-by gas into the engine inlet airflow. Thus, the blow-by gas once cleaned is directed to the enginecombustion 20 chamber for combustion of any oil remaining in the cooledblow-by gas and, equally importantly, combustion of any uncombusted fuelproducts contained within said gas. Thus, emissions from the engine 10due to burning of oil contained within blow-by gas is dramaticallyreduced.

Both of the embodiments hereinbefore described also have the advantageof recovering a substantial proportion of oil 40 which would ordinarilybe lost in the blow-by gas. It has surprisingly been found that bycooling the blow-by gas in the manner proposed an oil recovery rate ofup to 70% can be achieved.

FIG. 3 illustrates an preferred form of the heat exchanger 30 for use inthe apparatus according to the invention. This comprises a generallycylindrical housing 44 containing a plurality of tubular members 46which are arranged spaced apart in side-by-side relation with theirlongitudinal axes parallel with the longitudinal axis of the housing 44.The tubular members 46 are spaced within the housing 44 so as to providegaps 48 (FIGS. 4 and 5) therebetween and an outer space 50 (FIGS. 4 and5) between them and an inner wall 44a of the housing which together withpartition plates 52(a,b,c) which divide the space 50 define a flow pathfor blow-by gas between the blow-by gas inlet 30c and blow-by gas outlet30e of the heat exchanger 30. The tubular members 46 collectively definea flow path for the cooling agent which, in the preferred embodiment,comprises air from the engine inlet air system.

In the preferred embodiment, it will be seen that blow-by gas 34entering the blow-by gas inlet 30c of the heat exchanger 30 is forced toflow over the outer surfaces of first ends of the tubular members 46generally downwardly before rising over second ends of the tubularembers 46 towards the blow-by gas outlet 30e. The tubular members 46 arecooled by the air 42 from the engine inlet air system flowing throughthem. Consequently, the blow-by gas, which is at a temperature ofapproximately 70° C. on entry to the heat exchanger 30, is cooled toabout 20° C. during its passage between the blow-by gas inlet 30c andoutlet 30e. This results in a substantial proportion of oil vapourcontained within said blow-by gas condensing within the housing 44. Thecondensed oil collects in a base of the housing 44 before draining viathe oil drainpipe 36 back to the engine sump 16. The blow-by gas outlet30e directs cooled blow-by gas into the inlet air flow to be carried tothe engine inlet manifold for combustion.

The heat exchanger is arranged such that blow-by gas is generally forcedto flow in a direction opposite to that of cooling air from the engineinlet air system and the length of the blow-by gas flow path issubstantially greater than the length of the flow path of cooling airfrom the engine air cooling system. The tubular members 46 may becircular (FIG. 4) in cross-section some of which may include a fin 46ato increase the heat transfer surface area of the blow-by gas flow path.Preferably, the tubular members 46 are hexagonal and are arranged suchthat the gaps 48 therebetween are of constant width thus defining aplurality of minor flow paths for blow-by gas.

The partition plates 52(a,b,c) are arranged so as to secure the tubularmembers 46 in their spaced apart side-by-side relationship and areplaced within the housing 44 in order to divide the internal space 50 todefine around the exteriors of the tubular members 46 the flow path forthe blow-by gas. It can be seen that plates 52(b,c) have respectivecutaway sections comprising part of the blow-by gas flow path. Thus,where the tubular members are hexagonal in cross-section, the partitionplates have a honeycomb arrangement as illustrated if FIGS. 6a to 6c.

To increase yet further oil recovery from the blow-by gas, a meshmaterial 54 (FIG. 7) may be located at least adjacent the blow-by gasoutlet 30e of the heat exchanger 30 in order to "filter" any oildroplets being carried toward said outlet 30e by the blow-by gas. theblow-by gas.

The heat exchanger may incorporate a sump pressure regulating valve 56(FIG. 8) which avoids the need for installation of a pressure regulatingmeans elsewhere on the engine 10.

It will be appreciated that the features of the second (FIG. 7) andthird (FIG. 8) embodiments of the heat exchanger can be incorporatedtogether in a single heat exchanger for use in the apparatus accordingto the invention.

It will also be appreciated that a heat exchanger comprising a part ofthe apparatus of the present invention can take many forms and can becooled by any suitable cooling agent. For example, it is envisaged thatwith a marine engine the cooling agent will be sea water.

I claim:
 1. A method of reducing the oil content of blow-by gas in aninternal combustion engine, comprising the steps of: conveying blow-bygas (34) away from the engine crankcase (14) to a heat exchanger (30)cooled by air (42) from an engine air intake system; cooling saidblow-by gas (34) by passing it through said heat exchanger (30);returning oil condensed from said cooled blow-by gas (34) to the engine(10); and directing said cooled blow-by gas (34) into the flow of engineinlet air via a blow-by gas outlet (30e) which is located internally ofthe heat exchanger (30), characterised in that said blow-by gas outlet(30e) is located adjacent to an air inlet end (30b) of said heatexchanger (30).
 2. A method as claimed in claim 1, characterised in thatthe cooled blow-by gas (34) is directed into the flow of engine inletair (42) in a direction generally opposite to a direction of flow ofsaid inlet air.
 3. A method as claimed in claim 1, characterised in thatthe blow-by gas (34) is forced to flow through the heat exchanger (30)in a direction generally opposite to the direction of cooling air (42)flowing through said heat exchanger (30).
 4. A method as claimed inclaim 1, characterised in that it includes directing the cooled blow-bygas (34) into the engine inlet air flow (42) on an engine side of an airfiltering means of the engine air intake system.
 5. A method as claimedin claim 1, characterised in that it includes forcing the blow-by gas(34) to flow over the outer surfaces of a plurality of tubular coolingmembers (44) mounted within the heat exchanger (30), the tubular members(46) being cooled b the air (42) from the engine air intake systemflowing through them.
 6. A method as claimed in claim 5, characterisedin that it includes forcing the blow-by gas (34) to flow over the outersurfaces of first ends of said tubular members (46) before flowing overthe outer surfaces of second ends of said members (46).
 7. A method asclaimed in claim 1, characterised in that it includes regulating thepressure of the blow-by gas (34) by means of a pressure regulating valve(56) incorporated in the heat exchanger (30).
 8. A method as claimed inclaim 1, characterised in that it includes passing the blow-by gas (34)through a mesh material (54) located in the blow-by gas flow pathadjacent to the blow-by gas outlet (30e).
 9. A method as claimed inclaim 1, characterised in that it includes the step of returning oilcondensed from said cooled blow-by gas (34) to the engine sump (16). 10.A method as claimed in claim 1, characterised in that it includesreturning oil condensed from said cooled blow-by gas (34) to a positionin the sump (16) below the normal engine oil level.
 11. An apparatus forreducing the oil content of blow-by gas in an internal combustionengine, comprising: means for conveying blow-by gas (34) away from theengine crankcase (14) to a heat exchanger (30) cooled by air (42) froman engine air intake system, said blow-by gas (34) being cooled bypassing it through the heat exchanger (30); means (36) for returning oilcondensed from said cooled blow-by gas (34) to the engine (10); andmeans (30e) for directing the cooled blow-by gas (34) into the flow ofengine inlet air (42), said means (30e) comprising a blow-by gas outlet(30e) located internally of the heat exchanger (30), and characterisedin that said blow-by gas outlet (30e) is located adjacent to an inletair end (30b) of said heat exchanger (30).
 12. An apparatus as claimedin claim 11, characterised in that the blow-by gas outlet (30e) isarranged such that it directs cooled blow-by gas (34) into the flow ofengine inlet air (42) in a direction generally opposite to a directionof flow of said inlet air.
 13. An apparatus as claimed in claim 11,characterised in that the heat exchanger (30) is arranged such thatblow-by gas (34) is forced to flow through the heat exchanger (30) in adirection generally opposite to the direction of cooling air (42)flowing through said heat exchanger (30).
 14. An apparatus as claimed inclaim 11, characterised in that the heat exchanger (30) is arranged onan engine side of an air filtering means of the engine air intakesystem.
 15. An apparatus as claimed in claim 11, characterised in thatthe oil return means (36) returns condensed oil to a sump (16) of theengine (10).
 16. An apparatus as claimed in claim 15, characterised inthat the oil return means (36) returns condensed oil to a position onthe engine sump (16) below a normal engine oil level.
 17. An apparatusas claimed in claim 11, characterised in that it includes a pressureregulating valve (56) incorporated in the heat exchanger (30), saidvalve (56) being arranged to regulate the pressure of blow-by gas (34)being conveyed to the heat exchanger (30) from the engine crankcase(14).
 18. An apparatus as claimed in claim 11, characterised in that theheat exchanger (30) comprises a housing (44) containing at least onetubular member (46) arranged with its longitudinal axis parallel withthe longitudinal axis of the housing, said at least one tubular member(46) defining a flow path for the cooling air (42), and an inlet (30c)for blow-by gas which communicates with space (50) surrounding said atleast one tubular member (46) and partition plates (52) which dividesaid space (50) to define a flow path for the blow-by gas (34) extendingfrom said blow-by gas inlet (30c) to the blow-by gas outlet (30e)located internally of the heat exchanger (30).
 19. An apparatus asclaimed in claim 18, characterised in that the heat exchanger (30)includes a plurality of tubular members (46) arranged spaced apart inside by side relationship within the housing (44).
 20. An apparatus asclaimed in claim 19, characterised in that the tubular members (46) arecircular in cross-section.
 21. An apparatus as claimed in claim 19,characterised in that each tubular member (46) includes a fin (46a)extending from its outer surface, the fin (46a) acting as an additionalheat transfer means for cooling the blow-by gas (34).
 22. An apparatusas claimed in claim 19, characterised in that the tubular members (46)have a polygonal cross-section.
 23. An apparatus as claimed in claim 18,characterised in that the heat exchanger (30) includes a mesh material(54) located in the blow-by gas flow path adjacent to at least theblow-by gas outlet (30e).
 24. An internal combustion engine including anapparatus in accordance with claim 11.